1. Field of the Invention
This invention relates to shock tubes. More particularly, this invention relates to a new and improved device that will create a uniform dusty gas suspension in a shock tube.
2. Description of the Prior Art
In the study of chemical reactions of powdered materials at high temperatures and pressures, researchers have utilized reflected shock waves in shock tubes to study ignition and exposive behavior of energetic materials. Explosive limits and flammability of air suspensions of powdered coal, grain dust, propellants, etc. as functions of concentration and particle size can be determined by this technique. Since the shock waves are not visible but are instead a gradient of air pressure, suspensions of powder or dust created withn the shock tubes also provide a means of monitoring shock wave transients. Unless the powder or dust is uniformly distributed as a dusty gas adjacent the end wall of the shock tube, the interpretation of experimental results beomces considerably more difficult.
In the past, suspensions of dust or powders within gases have been produced in shock tubes by using the incident shock flow to disperse such powders placed upon aerodynamic foils having shapes such as a knife-edge or contoured disk. In another method, the suspension is produced by dispersing the powders from thin films. While these techniques are capable of generating a dusty gas in the test section of a shock tube, the powder cannot be uniformly distributed near the end wall and the time for formation of the suspension is controlled strictly by the incident shock wave itself. Thus, the test conditions are approximate at best.
In one previous method, an arrangement incorporating a vertically-oriented shock tube and a blower-and-solenoid valve assembly was used to produce a dusty gas in the shock tube chamber prior to initation of the shock wave. The solenoid valves, located on the side and end walls of the tube, are closed immediately before shock initiation. Placing a shock tube in a vertical plane and adding solenoids requires extensive modifications to the end-plate and sidewall, increasing overall cost and lessening the versatility of the test apparatus.